Catheters are often used in medical procedures to provide access to remote locations within a patient. A catheter can be inserted into the patient's body through a small incision and threaded through a blood vessel or other narrow passageway to reach the intended location. Dilatation catheters have been used to open blockages in blood vessels in percutaneous transluminal coronary angioplasty procedures, for example. Various types of catheters are also used in electrophysiology therapies to locate and treat cardiac arrhythmias. For example, one or more catheters may be used to pace, map and ablate cardiac tissue to block the passage of aberrant electrical signals.
Steering mechanisms have been developed to facilitate the transit of catheters through body lumens such as the vascular system. These mechanisms typically require that a physician or other trained medical professional hold and rotate the catheter to navigate the twists and branches of the body lumen. Movement of the steering assembly bends or deflects a distal portion of the catheter, allowing the physician to steer the catheter through the body lumen. In many applications, the ability to steer the catheter is critical to the success of the diagnostic or therapeutic protocol and may affect the risk of trauma to the patient as well. Moreover, the ability to precisely steer the catheter impacts the speed and ease by which the physician can properly position the distal portion of the catheter. Steering mechanisms are described in U.S. Pat. No. 6,163,716, which is incorporated by reference, herein, for example. Steering mechanisms are also described in U.S. Pat. No. 6,064,902, which is also incorporated by reference herein. Steering mechanisms have also been developed to control a catheter once it reaches its final destination. For example, steering mechanisms can be used to precisely position a catheter within the chambers of the patient's heart.
In a typical cardiac ablation procedure, electrical signals are applied to the cardiac tissue by a pacing catheter to induce arrythmia. A mapping catheter is then used to locate aberrant electrical pathways and currents emanating within the heart. The mapping catheter records the actuation times, the distribution and the waveforms of the electrical charges or potentials that trigger the pumping action of the heart muscle. The mapping catheter may be a “basket” catheter with a mapping basket at its distal end. The basket may comprise eight arms constructed of ribbons of a shape memory material, such as Nitinol. Each arm carries a plurality of mapping electrodes that detect the electrical activity of underlying cardiac tissue. A plurality of ultrasound receiving transducers are also mounted to each arm. Pacing and mapping catheters are described in U.S. Pat. No. 6,216,027 B1, for example, which is incorporated by reference herein.
After the aberrant electrical signals and pathways are located, lesions are formed in the cardiac tissue by an ablation catheter, to block the propagation of the aberrant electrical signals. The ablation catheter includes one or more energy transmitting elements, such as electrodes of gold, tantalum or platinum, to transmit energy, such as RF energy, to ablate the tissue to form the lesions. Ablation catheters are described in U.S. Pat. No. 6,241,724 B1, U.S. Pat. No. 6,216,027 B1, and U.S. Pat. No. 6,004,269, for example, which are assigned to the assignee of the present invention and are incorporated by reference herein. Two or more functions (pacing, mapping and/or ablation) may be provided on the same catheter, as described in U.S. Pat. No. 6,163,716, which is incorporated by reference herein.
Cardiac ablation systems typically include an imaging system to display the position of the one or more catheters used in the procedure. Ultrasound, magnetic, x-ray, or other imaging techniques known in the art may be used.
Cardiac Pathways Corporation, Sunnyvale, Calif., provides an Arrythmia Mapping System with Realtime Position Management™ Tracking Technology that enables the user to record, view and analyze intracardiac electrogram and EKG signals, as well as to view a realtime graphic representation of the catheters being used in the procedure. The views of the catheters may be rotated in three dimensions. A “time of flight” principle is used in combination with geometrical triangulation to establish a three-dimensional coordinate system using reference ultrasonic transducers on one or more reference catheters. Other catheters used in the procedure, such as the ablation catheter, include transducers to detect the ultrasound signals emitted by the reference transducers. Once the coordinate system is established, the three-dimensional location of the other catheters may be established by using the time of flight method to determine the distance between the catheter and the reference catheters. The coordinates of the catheter may then be established by basic algebra and the law of cosines, through triangulation. Operation of the Cardiac Pathways Arrythmia Mapping System is described in more detail in U.S. Pat. No. 6,216,027 B1, which is incorporated by reference herein. Cardiac Pathways Corporation has merged with Boston Scientific EP Technologies, Inc. San Jose, Calif.
It is often desirable to identify and store information concerning the procedure and the areas of the patient's heart that had been ablated or are currently being ablated. This information can include certain characteristics of the ablation procedure such as the temperature of the ablation electrode during the ablation procedure and the type of lesions that are formed. The date of the procedure may be recorded, as well. Some advanced ablation systems, such as the Cardiac Pathways system described above, are capable of identifying and storing this information.
Some ablation systems have the capability to color code certain information about a procedure. For example, cardiac tissue ablated in prior procedures may be identified by one color, such as yellow, while cardiac tissue ablated in the current procedure may be identified by a second color, such as green. In this way, the physician can readily distinguish between current ablation sites and earlier ablation sites. Likewise, the physician can assign color based on the power of the electrodes during the ablation process and is then capable of distinguishing between these ablation areas based on the color. The use of several colors may also assist the physician in his performance of an ablation procedure. For example, the use of two colors contrasts the different procedures. This can assist the physician by ensuring that the ablation areas of two different ablation procedures at least partially coincide with each other when such result is desired.
One drawback of conventional catheters, including catheters used in ablation procedures, is that they may require both of the physician's hands to hold the catheter and manipulate the steering assembly. In electrophysiology procedures, the initiation and completion of the pacing, mapping and ablation procedures, as well as color coding, for example, require input to a control device by an input device, such as a keyboard. Since the physician does not have a free hand to operate the keyboard or other such input device, the physician must verbally instruct others to operate the input device to initiate and complete these and other functions. Verbal instructions may be misunderstood and, in some instances, may be hard to communicate. In addition, there is a time delay between the giving of the verbal instruction and the performance of the request. At least one extra person may be required in the operating room to carry out the physician's instructions, increasing the costs of the procedure and increasing the likelihood of error.
Certain prior art ablation catheters include a handle with one or more buttons to control the powering up and powering down of an RF generator to provide energy to the one or more electrodes near the distal end of the catheter. See, for example, U.S. Pat. No. 6,142,994, which is incorporated by reference, herein. These buttons provide the physician with the ability to directly initiate ablation of cardiac tissue while holding the catheter. Other functions are not directly controlled by the physician conducting the ablation procedure, but by an assistant operating an input device, as discussed above.